Hexamethyltriethylenetetramine Research Articles

N-substituted methyl ethylenediamine derivatives as corrosion inhibitors for carbon steel in 1 M hydrochloride acid

Three N-substituted methyl ethylenediamine derivatives, tetramethylethylenediamine (TDA), pentamethyldiethylenetriamine (PTA), and hexamethyltriethylenetetramine (HTA) were prepared for the corrosion inhibition of 20# steel in 1 M HCl solution. Their corrosion inhibition properties were investigated using weight loss, potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS) measurements, and surface analysis techniques. Quantum chemical calculations and molecular dynamics (MD) simulations were applied to analyze the molecular structure-activity relationship of corrosion inhibitors. The results indicated that all three methyl ethylenediamine derivatives exhibited excellent inhibition properties. The order of inhibition efficiency of these inhibitors was TDA < PTA < HTA. Furthermore, all three inhibitors act as mixed-type inhibitors and mainly inhibited the cathodic reaction. The adsorption mechanism of corrosion inhibitors follows the Langmuir isotherm and proceeds by physisorption and chemisorption. The results of quantum chemical calculations and MD simulations effectively support the experimental results. The excellent corrosion inhibition property is attributed to the interaction between tertiary amine groups and Fe, which effectively inhibits corrosion.

Durable antibacterial and UV protections of in situ synthesized zinc oxide nanoparticles onto cotton fabrics

Herein we represent a new discovery based on amine material called hexamethyltriethylene tetramine (HMTETA). We have observed that when an aqueous solution of Zn(NO3)·6H2O was added to aqueous solution of HMTETA followed by shaking for a time, the colorless solution was converted to milky color under the alkaline medium provided by HMTETA prior to formation of uniform zinc oxide nanoparticles (ZnO NPs). The latter are in situ formed within the cotton fabrics without the support of capping or other stabilizing agents. Obviously, then, the new made of formation of ZnO NPs speaks of a single-stage process where cotton fabric is immersed in a prepared solution of the new precursors through which binding of ZnO NPs into the textile fabrics takes place. Textile fabrics are, indeed, used as a template, which is capable of maintaining the size and surface distribution of the as-synthesized nanoparticles in a uniform domain. It is also likely that nanoparticles is confined inside the fibril and microfibrils of the cotton fibers. World-class facilities have been employed to follow up the synthesis of ZnO NPs, their characterization and their application to confer, in particular, high durable antibacterial and UV protective function on cotton fabrics.

Exploration of Novel Pyrene Labeled Amphiphilic Block Copolymers: Synthesis Via ATRP, Characterization and Properties

A novel initiator containing pyrene, a fluorescent moiety, was prepared by reacting 1-aminopyrene and 2-bromoisobutyl bromide. The structure elucidation of the new initiator was carried out using various spectroscopic tools, as well as through single crystal X-ray diffraction studies. Novel, fluorescent amphiphilic block copolymers with a pyrene end-group, poly(styrene-b-acrylic acid) [P(S-b-AA)], poly(methyl methacrylate-b-dimethylaminoethyl methacrylate) [P(MMA-b-DMAEMA)], poly(styrene-b-tert-butyl acrylate) [P(S-b−t-BA)], poly(styrene-b-dimethylaminoethyl methacrylate) [P(S-b-DMAEMA)] were successfully synthesized by the atom transfer radical polymerization (ATRP) method, using CuBr as the catalyst and N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA)/N,N,N′,N″,N″-hexamethyltriethylenetetramine (HMTETA) as the complexing agent. The polymers were characterized by GPC, 1H-NMR, IR and UV-Vis spectroscopies. It was observed that as the polymerization time increased, both the conversion and the molecular weight increased linearly with time. The fluorescence properties of the polymers prepared were recorded. The physical properties and especially the pH dependent swelling properties of the amphiphilic block copolymers have been investigated. The utility of the block copolymers in the formation of stable dispersion of cadmium sulphide nanoparticles was investigated as a model study.

Synthesis of brush-like copolymers using carbohydrates as initiators: Benefits of organic catalysts for the ROP of lactones

New brush-like copolymers have been synthesized using functional polymethacrylate backbones bearing pendant sugars. Ring-opening polymerization (ROP) of l-lactide and ε-caprolactone have been performed using 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) carbohydrate residues on the polymethacrylate chains. The latter have been first synthesized by copolymerization of three methacrylate monomers including methyl methacrylate (MMA), α-methoxy, ω-methacrylate poly(ethylene oxide) (MAPEO), and 1,2:3,4-di-O-isopropylidene-6-O-methacryloyl- d-galactopyranose (MAIGP) by atom transfer radical polymerization (ATRP) in toluene at 80 °C using CuBr ligated with 1,1,4,7,10,10 hexamethyltriethylenetetramine (HMTETA) as catalytic complex. The protected sugars have been selectively deprotected using an aqueous solution of formic acid. The molecular characterization of those copolymers was performed by 1H-NMR spectroscopy, FT-IR spectroscopy and gel permeation chromatography (GPC) analysis.

Preparation of CuO Hollow Spheres by Oxidation of Cu Microspheres

Copper oxide (CuO) is a p-type semiconductor with narrow band-gap of 1.2 eV and is widely used as a photoconductive material, and in gas sensors and heterogeneous catalysts. Various morphologies of CuO, such as rods, wires, ribbons, spheres, and even dandelions have been obtained via different synthesis routes. Hollow microparticle CuO structures are probably of most interest due to their potential applications as catalysts, because of their low densities and large surface areas. Hardand soft-templates are commonly used to fabricate hollow copper oxides structures. Hollow CuO microspheres have been prepared hydrothermally from copper acetate as a precursor, and by a hydrothermal reaction using a coppercomplex, in which hexamethyltriethylenetetramine (HMTA) was used as a complexing reagent. Dandelion-like CuO hollow microparticles were also produced, via a donut-like intermediate assembly that consisted of equatorial stacks of rhombic CuO strips, by hydrothermal reaction between copper nitrate and NaOH. The simplest method of making CuO is by the direct oxidation of copper metal in air. Many research groups have prepared CuO nanowires and nanotubes by oxidizing copper nanowires and foils. However, it is difficult to obtain copper metal microspheres for the preparation of hollow CuO microspheres by direct thermal oxidation. Here, we describe a straightforward method for preparing hollow CuO microspheres with radially projecting surface nanorods via the direct thermal oxidation of copper metal microspheres. The morphologies of CuO microspheres and the mechanism of their formation are discussed.

Proton-Conducting Polymers via Atom Transfer Radical Polymerization of Diisopropyl-p-Vinylbenzyl Phosphonate and 4-Vinylpyridine

Copolymerization of diisopropyl-p-vinylbenzyl phosphonate (DIPVBP) and 4-vinylpyridine (4VP) by atom transfer radical polymerization (ATRP) was studied in the presence of different catalyst systems using DMF as solvent. When a CuIBr complex was used as catalyst and the reaction was carried at 90 °C in DMF, dramatically fast radical termination was observed and the chain propagation was almost stopped at an early stage of ATRP. CuICl with different ligands were used as ATRP catalyst systems to modify the reaction conditions. An improved ATRP catalyst system was CuICl/N,N,N′,N′′,N′′′,N′′′-hexamethyltriethylenetetramine (HMTETA). The 1H NMR technique was successfully applied online to investigate the kinetic parameters of atom transfer radical copolymerization (ATRCP) of DIPVBP and 4VP. The reactivity ratio of DIPVBP (rDIPVBP) and 4VP (r4VP) was 0.69 and 1.17, respectively, which were calculated with the Extended Kelen−Tudos method at high conversions (15−40%). A proton-conducting statistical copolymer (poly(vinylbenzyl phosphonic acid-stat-4VP)) was then obtained by complete hydrolysis of the phosphonate groups.

Carbohydrate-based amphiphilic diblock copolymers: Synthesis, characterization, and aqueous properties

Amphiphilic poly(ε-caprolactone)-b-poly[(methacrylate-graft-poly(ethylene oxide))-co-6-O-methacryloyl-D-galactopyranose] (PCL-b-P(MAPEO-co-GaMa)) with various compositions and molecular weights were synthesized via a controlled four-step strategy. The first step involves the synthesis of functionalized poly(ε-caprolactone) macroinitiator by ring-opening polymerization (ROP) of ε-caprolactone (CL) as initiated by aluminum triisopropoxide (Al(OiPr)3). After selective bromination of the hydroxyl end-group of the resulting α-isopropoxy, ω-hydroxy poly(ε-caprolactone) by using 2-bromoisobutyryl bromide, the controlled radical copolymerization of α-methoxy, ω-methacrylate poly(ethylene oxide) (MAPEO) with 6-O-methacryloyl-1,2;3,4-di-O-isopropylidene-D-galactopyranose (DIGaMa) was performed by atom transfer radical polymerization (ATRP) in THF at 60 °C using CuBr ligated with 1,1,4,7,10,10 hexamethyltriethylenetetramine (HMTETA) as catalytic complex. In the final step, isopropylidene protective functions were selectively removed using an aqueous formic acid solution leading to the expected amphiphilic graft copolymers. The molecular characterization of those copolymers was performed by 1H NMR spectroscopy and gel permeation chromatography (GPC) analysis. The self-assembly of the copolymers into micellar aggregates as well as the related critical micellization concentration (CMC) in aqueous media were determined by dynamic light scattering (DLS) and fluorescence spectroscopy, respectively. In parallel, the morphology of the solid deposits of micellar aggregates was examined with atomic force microscopy (AFM). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3662–3672, 2008

Controlled Radical Polymerization of Furfuryl Methacrylate

AbstractAtom transfer radical polymerization provides a new method of controlled radical polymerization. The most important advantage of ATRP is that it is tolerant to the different functional groups present in the initiator as well as in the monomer. Furfuryl Methacrylate (FMA) is a specialty monomer, which has applications in coatings, adhesives and in biomedicals. Conventional radical polymerization of FMA leads to excessive gel formation, which limits its applications. In this investigation homo and co‐polymerization of FMA has been carried out via ATRP. ATRP of FMA was carried out using CuBr as catalyst and 1, 1, 4, 7, 10, 10 hexamethyltriethylenetetramine (HMTETA) as ligand. There was no gel formation during the polymerization. ATRP of FMA was well controlled with a linear increase of molecular weight (Mn) with monomer conversion. The polymers were characterized by using 1HNMR, FT‐IR and GPC analysis. Interestingly, it was observed that the furfuryl ring was not affected during polymerization.

Atom transfer radical polymerization of styrene using a copper catalyst with a pseudohalogen anion

AbstractAtom transfer radical polymerization has been a very useful method in the recent advances in controlled radical polymerization. It needs an activated alkyl halide as an initiator and a copper halide as a catalyst. This investigation reports the successful application of copper thiocyanate, a catalyst with a pseudohalide anion, in the presence of different ligands such as N,N,N=,N″,N‴,N‴‐hexamethyltriethylenetetramine (HMTETA), pentyl‐2‐pyridylmethaneimine, and substituted bipyridine in the atom transfer radical polymerization of styrene. Among the three ligands used, HMTETA was found to be very efficient. The polymers were characterized with 13C‐NMR, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry, and gel permeation chromatography analysis. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1418–1426, 2005

Amphiphilic poly( N, N-dimethylamino-2-ethyl methacrylate)-g-poly(ε-caprolactone) graft copolymers: synthesis and characterisation

Amphiphilic poly( N, N-dimethylamino-2-ethyl methacrylate)-g-poly(ε-caprolactone) graft copolymers (PDMAEMA-g-PCL) with various compositions and molecular weights were synthesised via a fully controlled three-step strategy. First, poly(ε-caprolactone) macromonomers (PCLMA) were prepared by ring-opening polymerization (ROP) of ε-caprolactone (CL) initiated by aluminum triisopropoxide (Al(O i Pr) 3), followed in a second step by quantitative esterification of PCL hydroxy end-groups with a methacrylic acid derivative. Finally, the controlled copolymerization of PCLMA and N,N-dimethylamino-2-ethyl methacrylate (DMAEMA) was carried out by atom transfer radical polymerisation (ATRP) in THF at 60 °C using CuBr ligated with 1,1,4,7,10,10, hexamethyl triethylenetetramine and ethyl 2-bromoisobutyrate as catalyst and initiator, respectively. Furthermore, PDMAEMA-g-PCL graft copolymers were reacted with methyl iodide to convert the pendant tertiary amines into quaternary ammonium iodides increasing accordingly their water solubility. Some preliminary experiments was further carried out by tensiometry and dynamic light scattering in order to shed so light on the tensioactive behaviour of these amphiphilic graft copolymers (with protonated amines or quaternary ammonium cations).

ATRP of (meth)acrylates initiated with a bifunctional initiator bearing trichloromethyl functional groups and structural analysis of the formed polymer

ATRP of methyl methacrylate (MMA), initiated with 1,3-bis{1-methyl-1-[(2,2,2-trichloroethoxy)carbonylamino]ethyl}benzene as a bifunctional initiator (BI) under CuCl catalysis was studied in the presence of 2,2′-bipyridine (bpy) or hexamethyltriethylenetetramine (HMTETA) ligands, in bulk or in toluene. With the bpy, the polymerization reaches only limited monomer conversions and products have broad MWDs. In contrast, polymerization in the presence of HMTETA is a well-controlled process, affords virtually quantitative conversion, giving PMMAs with narrow MWDs and predictable molecular weights within a range of more than one order of magnitude. NMR analysis of the prepared PMMA proved formation of linear polymers with im-measurable extent of chain branching or β-scission as undesired side reactions. The prepared α,ω-dichloro-PMMAs were used as macroinitiators for ATRP of tert-butyl acrylate ( t-BuA), giving the corresponding triblock copolymers with narrow MWDs and molecular weights controllable in a wide range. Block copolymerizations were performed in dimethyl formamide (DMF) or acetone in the presence of pentamethyldiethylenetriamine (PMDETA) as ligand and could be accelerated by addition of metallic copper.

“Controlled” Synthesis and Characterization of High Molecular Weight Methyl Methacrylate/tert-Butyl Methacrylate Diblock Copolymers via ATRP

Atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) using CuCl/N,N,N‘,N‘ ‘,N‘ ‘‘,N‘ ‘‘-hexamethyltriethylenetetramine (HMTETA) as a catalyst system with 2,2,2-trichloroethanol (TCE) as initiator was investigated. Poly(methyl methacrylate) (PMMA) macroinitiators with defined molecular weight, low polydispersity index (PDI), and a high end-group functionality were obtained. These PMMA macroinitiators successfully initiate block copolymerization of tert-butyl methacrylate (tBMA), resulting in poly(MMA-b-tBMA) diblock copolymers with low PDI for a range of tBMA block lengths. Gradient polymer elution chromatography (GPEC) was used to confirm the block copolymer structure. Furthermore, the effect of molecular weight of the macroinitiator, nature of catalyst system (heterogeneous/homogeneous), and the amount of solvent on the degree of control achieved in the block copolymerization was studied. The GPEC technique was successfully used to demonstrate the effect of the aforementioned parameters on the block copolymer structure. In particular, the use of a homogeneous catalyst system, CuBr/4,4‘-di-5-nonyl-2,2‘-bipyridine (dNbpy), and a large ratio of methyl ethyl ketone (MEK) to PMMA macroinitiator led to the synthesis of well-controlled high molecular weight diblock copolymers. This can be explained by the complete solubility of the Cu(II) complex, the deactivating species in the ATRP mechanism. The use of the dNbpy ligand and the polar solvent (MEK) promotes the homogeneous catalyst conditions. The homogeneous condition leads to efficient activation/deactivation exchange reactions between the growing polymer chains and the dormant polymer chains, resulting in well-controlled block copolymers.

Continuous atom transfer radical block copolymerization of methacrylates

AbstractA column reactor packed with silica‐gel‐supported copper bromide (CuBr)–hexamethyltriethylenetetramine (HMTETA) was developed for the continuous‐transition–metal‐mediated living/controlled radical polymerization [atom transfer radical polymerization (ATRP)] for homo‐ and block copolymerization of methyl methacrylate (MMA). The reactor showed good stability (&gt;100 h) in both catalyst activity and molecular weight of the poly(methyl methacrylate) (PMMA) produced. The MMA conversion decreased as the flow rate increased. The polymerization in the reactor was in first order with respect to monomer concentration. The molecular weight of the resulting PMMA increased linearly with MMA conversion, exhibiting the characteristic feature of living polymerization. Thus, simply changing the flow rate of MMA, which in turn determined the MMA conversion, readily controlled the molecular weight of PMMA. The block copolymerization of MMA with n‐butyl methacrylate (nBMA) was carried out using two reactors connected in series. The block copolymers were slightly contaminated by PMMA prepolymer from the first column. The molecular weight of the nBMA block could be changed by the flow rate of the nBMA in the second reactor. This packed column reactor technology is feasible for continuously synthesizing polymers or block copolymers with controlled molecular weights that are readily adjustable by changing the monomer flow rates.

Atom Transfer Radical Polymerization of Methyl Methacrylate by Silica Gel Supported Copper Bromide/Multidentate Amine

A silica gel support system for the copper bromide−hexamethyltriethylenetetramine (HMTETA) complex was successfully developed for the atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) in toluene. The supported complex mediated a living polymerization of MMA, yielding polymers with controlled molecular weights and narrow molecular weight distributions. The MMA concentration had significant influence on the polymerization behavior. At 33% MMA concentration, the polymerization catalyzed by CuBr−HMTETA/silica gel followed typical first-order kinetics with respect to the monomer. But at 50% MMA, the polymerization significantly deviated from the first-order kinetics after the MMA conversion reached 30%. The supported catalysts were recycled for second and third uses. The recycled catalysts remained 80% active in the second use and 50% in the third use relative to their initial activity. The recycled catalysts had even better controllability over the polymerization. The molecular weights of PMMA produced agreed with the predicted values, and the polydispersities were less than 1.2.

Complexes of 9-propylfluorenyl ion pairs with tertiary polyamines in apolar solvents

The complexation of tetramethylethylenediamine (TMEDA), hexamethyltriethylenetetramine (HMtT) and tetramethyltetraazacyclotetradecane (TMTCT) with ion airs of 9-(n-propyl)fluorenyllithium (PFl −, Li +) and n-butyl-9-(n-propyl)fluorenylmagnesium (BuPFlMg) in cyclohexane was studied by optical spectroscopy. The results can be explained in terms of externally complexed tight ion pairs and ligand-separated ion pairs, the latter complexes being much less soluble. With HMTT and PFl −, Li +, the only complexes formed are (PFl −, Li +) 2 HMTT (λ m 357 nm) and PFl −, HMTT, Li + (λ m 383 nm). The reaction of PFl −, Li +, TMEDA with TMTCT to form the loose ion pair complex PFl −, TMTCT, Li + has a rate constant in toluene of 250 M −1 sec −1. With the magnesium compound, the amines form only a loose ion pair complex, e.g., BuMg +, TMEDA, PFl − (λ m 382 nm).